Radar altimeter antenna performance monitoring via reflected power measurements

Abstract

Systems and methods for radar altimeter antenna performance monitoring via reflected power measurements are provided. In one embodiment, a single antenna radar altimeter comprises: an antenna; a circulator coupled to the antenna; a transmitter coupled to the circulator; a receiver coupled to the circulator; wherein the circulator provides coupling of the transmitter and the receiver to the antenna while providing isolation between the transmitter and the receiver; a reflected power monitor positioned between the circulator and receiver; and a processor coupled to the reflected power monitor via a first analog-to-digital converter, the processor configured to compute and track reflected power measurement statistics from data generated by the reflected power monitor and provide a performance output indicating when one or more of the reflected power measurement statistics exceed a predetermined deviation threshold.

1. A method for determining radar altimeter antenna performance, the method comprising:
 measuring a reflected power from an antenna of a single antenna radar altimeter; 
 computing and tracking reflected power measurement statistics from the reflected power from the antenna; 
 evaluating changes in reflected power measurement statistics to identify a static event failure condition; 
 providing a Failure Warning (FW) override response when a static event failure condition is identified; 
 evaluating changes in a reflected power measurement statistics to identify a dynamic event condition; and 
 providing a No Computed Data (NCD) override response when a dynamic event failure condition is identified. 
 
     
     
       2. The method of  claim 1 , wherein computing and tracking reflected power measurement statistics comprises computing and tracking at least a maximum reflected power measurement statistic for the antenna, a minimum reflected power measurement statistic for the antenna, and a Δreflected power max-min  measurement statistic for the antenna. 
     
     
       3. The method of  claim 1 , wherein measuring a reflected power further comprises collecting reflected power measurement samples as sample group collected over a period equal to a modulation period of the single antenna radar altimeter. 
     
     
       4. The method of  claim 1 , wherein computing and tracking reflected power measurement statistics further comprises collecting a plurality of sample groups, each of the plurality of sample groups collected over a period equal to a modulation period of the single antenna radar altimeter, and wherein the reflected power measurement statistics are computed for each of the plurality of sample groups. 
     
     
       5. The method of  claim 4 , further comprising evaluating changes in reflected power measurement statistics for a current sample group of the plurality of sample groups against at least one previous sample group of the plurality of sample groups. 
     
     
       6. The method of  claim 5 , wherein evaluating changes in reflected power measurement statistics includes evaluating changes in at least one of maximum reflected power and average reflected power. 
     
     
       7. The method of  claim 4 , further comprising evaluating changes in a Δreflected power max-min  measurement statistics for a current sample group of the plurality of sample groups against at least one previous sample group of the plurality of sample groups. 
     
     
       8. The method of  claim 1 , further comprising measuring a transmitted power to the antenna of the single antenna radar altimeter; and
 evaluating changes in reflected power measurement statistics against changes in transmitted power measurement statistics. 
 
     
     
       9. The method of  claim 1 , wherein a static event failure condition is identified based on when at least one of a maximum reflected power statistic or an average reflected power statistic exceed a threshold value. 
     
     
       10. The method of  claim 1 , wherein a dynamic event condition is identified based on when a Δreflected power max-min  measurement statistic exceeds a threshold value. 
     
     
       11. A single antenna radar altimeter, the altimeter comprising:
 an antenna; 
 a circulator coupled to the antenna; 
 a transmitter coupled to the circulator; 
 a receiver coupled to the circulator; wherein the circulator provides coupling of the transmitter and the receiver to the antenna while providing isolation between the transmitter and the receiver; 
 a reflected power monitor positioned between the circulator and receiver; 
 a transmitted power monitor positioned between the circulator and transmitter; and 
 a processor coupled to the reflected power monitor via a first analog-to-digital converter, the processor configured to compute and track reflected power measurement statistics from data generated by the reflected power monitor and provide a performance output indicating when one or more of the reflected power measurement statistics exceed a predetermined deviation threshold; 
 the processor further coupled to the transmitted power monitor via a second analog-to-digital converter, the processor configured to compute and track transmitted power measurement statistics from data generated by the transmitted power monitor and provide a performance output indicating a condition of the antenna based on comparing changes in the reflected power measurement statistics against changes in the transmitted power measurement statistics. 
 
     
     
       12. The altimeter of  claim 11 , wherein the processor computes and tracks reflected power measurement statistics that include one or more of a maximum reflected power, a minimum reflected power, a Δreflected power max-min  and an average reflected power. 
     
     
       13. The altimeter of  claim 11 , wherein the processor collects samples of reflected power measurements as a plurality of sample groups, each sample group comprising samples collected over a sampling period that is equal to a radar modulation period used by the transmitter. 
     
     
       14. The altimeter of  claim 13 , wherein the processor evaluates changes in reflected power measurement statistics by evaluating changes in reflected power measurement statistics for a current sample group of the plurality of sample groups with at least one previous sample group of the plurality of sample groups. 
     
     
       15. The altimeter of  claim 11 , wherein the processor is configured to provide a performance output indicating a failure warning (FW) override signal when at least one of a maximum reflected power measurement statistic or an average reflected power measurement statistic exceed a threshold value. 
     
     
       16. The altimeter of  claim 11 , wherein the processor is configured to provide a performance output indicating a No Computed Data (NCD) override when a Δreflected power max-min  measurement statistic crosses a threshold value. 
     
     
       17. A system for determining radar altimeter antenna performance, the system comprising:
 a processor having access to memory; and 
 an analog to digital converter coupled to a radar frequency reflected power monitor, wherein the radar frequency reflected power monitor outputs a reflected power measurement representing power reflected from an antenna for a single antenna radar altimeter; 
 wherein the processor collects samples of reflected power measurements into a plurality of sample groups, each of the sample groups comprising a plurality of reflected power measurements captured over a period of time corresponding to a radar modulation period for radar transmissions from the single antenna radar altimeter; 
 wherein the processor computes reflected power measurement statistics for each of the plurality of sample groups, and stored the reflected power measurements statistics into the memory; and 
 wherein the processor tracks the reflected power measurements over time and outputs at least one override signal when the reflected power measurements are determined by the processor to characterize an event indicating a degradation affecting the antenna of the single antenna radar altimeter. 
 
     
     
       18. The system of  claim 17 , wherein the processor outputs a first override signal based on changes in one or both of maximum reflected power statistics over time, or average reflected power measurement statistics, over time. 
     
     
       19. The system of  claim 18 , wherein the processor outputs a second override signal based on changes in Δreflected power max-min  measurement statistics over time.